Process for fabrication of seamless uv cured intermediate transfer belts (itb)

ABSTRACT

Various embodiments provide methods and apparatus for forming intermediate transfer belts (ITBs) by combining a dip-coating process with a UV-curing process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/832,322, filed Jul. 8, 2010, which is incorporated herein byreference in its entirety.

FIELD OF THE USE

The present teachings relate generally to intermediate transfer belts(ITB) used for electrostatographic devices and, more particularly, tomethods and apparatus for forming ultraviolet (UV) cured ITBs.

BACKGROUND

Conventional materials for ITBs include polyimide resins. The polyimideresins include thermoplastic polyimide resins and thermosettingpolyimide resins. Conventional ITBs are fabricated either by flowcoating, dip coating, extrusion molding or centrifugal molding followedby a heating process for a long period of time. For example,conventional polyimide-based ITBs are usually formed by heating attemperatures greater than 300° C. for more than 1 hour. During thisheating process, coating solvents are evaporated and are often releasedinto the environment. While conventional polyimide-based ITBs can bemade seamed or even seamless, faster and cleaner fabrication processesare desired,

It is also desirable to control the thickness of ITBs. Conventionalmethods to form belts of desired thickness include a multiple coatingprocess that forms a first coating layer. Subsequently, additionalcoating layers are formed on the first coating layer until the desiredthickness is reached. Problems arise with this conventional methodbecause solvents used to form the subsequent coating layers can dissolvepreviously formed coating layers.

Thus, there is a need to overcome this and other problems of the priorart and to provide methods and apparatus for forming ITBs.

SUMMARY

According to various embodiments, the present teachings include a methodfor forming an intermediate transfer belt (ITB). The ITB can be formedby first providing a liquid coating composition that includes a UVcurable polymer. An ITB substrate can then be dip-coated in the liquidcoating composition to form a coating composition covered ITB substrate.After removed from the liquid coating composition, the coatingcomposition covered ITB substrate can be UV-cured to form a coatinglayer on the ITB substrate.

According to various embodiments, the present teachings also include anintermediate transfer belt (ITB). The ITB can include one or morecoating layers stacked together with each coating layer including a UVcured polymer. The ITB can have a surface resistivity ranging from about10⁸ ohms/sq to about 10¹³ ohms/sq, and a thickness ranging from about 30microns to about 500 microns with a thickness uniformity within a rangeof ±about 3 microns.

According to various embodiments, the present teachings further includean apparatus for forming an intermediate transfer belt (ITB). Theapparatus can include a dip tank configured to contain a liquid coatingcomposition and a UV-curing chamber configured on the dip tank toprovide a path for an ITB substrate to be immersed into the liquidcoating composition for a dip-coating and to enter the UV-curing chamberfor a UV-curing upon exiting the dip tank after the dip-coating. Theliquid coating composition contained in the dip tank can include a UVcurable polymer and a plurality of conductive materials.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the present teachings, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thepresent teachings and together with the description, serve to explainthe principles of the present teachings.

FIG. 1 is a schematic showing an exemplary apparatus forming an ITB inaccordance with various embodiments of the present teachings.

FIGS. 2A-2B depict exemplary ITB(s) formed on a substrate in accordancewith various embodiments of the present teachings.

It should be noted that some details of the figures have been simplifiedand are drawn to facilitate understanding of the embodiments rather thanto maintain strict structural accuracy, detail, and scale.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the presentteachings, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In thefollowing description, reference is made to the accompanying drawingsthat form a part thereof, and in which is shown by way of illustrationspecific exemplary embodiments in which the present teachings may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the present teachings and itis to be understood that other embodiments may be utilized and thatchanges may be made without departing from the scope of the presentteachings. The following description is, therefore, merely exemplary.

Various embodiments provide methods and apparatus for formingintermediate transfer belts (ITBs). In one embodiment, ITBs can beformed by a UV-curing process in conjunction with a dip-coating process.ITBs formed by this exemplary process can be seamless, and can beheterogeneous and/or homogeneous. Due to the combination of UV-curingwith dip-coating, the thickness of the ITBs formed using the disclosedmethod can be controlled. This differs from conventional methods offorming ITBs in which there is little control over the thickness.

FIG. 1 is a schematic showing an exemplary apparatus 100 for forming anITB in accordance with various embodiments of the present teachings. Itshould be readily apparent to one of ordinary skill in the art that theapparatus 100 represents a generalized schematic illustration and thatother components can be added or existing components can be removed ormodified.

As shown in FIG. 1, the apparatus 100 can include a dip tank 110, and aUV-curing chamber 130 attached to the dip tank 110, for example,configured on the dip tank 110. In embodiments, the dip tank 110 and theUV -curing chamber 130 can be configured to provide a path for asubstrate 120 (also referred to herein as “an ITB substrate”) to movebetween the UV-curing chamber and the dip tank, for example, to undergoa UV illumination and a dip-coating, respectively.

For example, to perform a dip coating, the substrate 120 can be immersedinto a liquid coating composition 105 contained in the dip tank 110 fora period of time to form a coating composition covered substrate, whichcan then be removed or withdrawn from the liquid coating composition105. When exiting the dip tank. 110, the coating composition covered (orcoated) substrate can enter the UV-curing chamber 130 for a UV-curingprocess. In embodiments, the apparatus 100 can be configured to allowmultiple cycles of dip-coating and UV-curing such that a desiredthickness can be obtained for the forced ITB coating layer.

The thickness of the final ITB coating layer can range, for example,from about 10 micron to about 500 microns, or from about 30 microns toabout 400 microns, or from about 50 microns to about 200 microns, forexample, from about 70 to about 120 microns, although other thicknessesare contemplated.

Referring back to FIG. 1, the liquid coating composition 105 can includeone or more UV curable polymers including, but not limited to, monomericacrylates, oligomeric acrylates and/or combinations thereof.

In embodiments, monomeric acrylates can function as co-reactants and/ordiluents in the composition to adjust system viscosity. The monomericacrylates can include, for example, trimethylolpropane triacrylates,hexandiol diacrylates, tripropyleneglycol diacrylates, dipropyleneglycoldiacrylates, etc.

In embodiments, oligomeric acrylates can be viscous liquid polymers withthe molecular weight ranging from several hundreds to several thousandsor higher. The oligomeric acrylates can include, for example, urethaneacrylates, polyester acrylates, epoxy acrylates, polyether acrylates,and olefin acrylates such as polybutadiene acrylates, etc.

The liquid coating composition 105 can also include photoinitiators,such as, for example, a photoinitiator for a surface curing of the UVcurable polymer, a photoinitiator for a bulk curing through the UVcurable polymer, and combinations thereof. In an exemplary embodiment,combined photoinitiators can be used to initiate the curing process.Examples of the photoinitiators can include, but are not limited to,acyl phosphines, α-hydroxyketones, benzyl ketals, α-aminoketones, andmixtures thereof.

In embodiments, the photoinitiators can be in a form of, for example.crystalline powders and/or a liquid. The photoinitiators can be presentin an amount sufficient to initiate the curing process of the UV curablepolymer(s). For example, the photoinitiators can be present in an amountranging from about 0.5% to about 10%, or from about 1% to about 7%, orfrom about 2% to about 5% by weight of the UV curable polymer(s).

In embodiments, the liquid coating composition 105 can be heterogeneousand can include UV curable polymer(s) and conductive fillers dispersedin the composition. The coating layer formed on the substrate 120 fromthe heterogeneous coating composition can be a heterogeneous layer,e.g., a heterogeneous ITB, including conductive fillers dispersed in UVcured polymer resins. The conductive fillers can be conductive and/orsemi-conductive.

The conductive fillers can include, but are not limited to, carbonblacks such as contactive furnace carbon blacks and acetylene blacks,carbon nanotubes, fullerenes (e.g., C₆₀ and C₇₀), polyanilines, stannicoxides, indium oxides, tin oxide, titanium oxide, antimony tin oxide,indium tin oxide, zinc oxide, potassium titanates and/or other types ofconductive and semi-conductive powders.

In embodiments, the heterogeneous coating composition can be prepared byball milling the conductive fillers in a liquid UV curable polymer, andthen adding corresponding photoinitiators into the milled dispersion.The final heterogeneous ITB coating layer can include conductive fillersranging from about 0.1% to about 50%, or from about 1% to about 30%, orranging from about 3% to about 20% by weight of the total heterogeneousITB coating layer.

Alternatively, the liquid coating composition 105 can be homogeneous andcan include UV curable polymers and conductive species that are soluble,compatible, or miscible with the UV curable polymers. The homogeneousliquid composition can be dip-coated on the substrate 120 and can form aUV cured homogeneous ITB coating layer. In embodiments, the ITB coatinglayer can have uniform electrical resistivities in bulk and/or onsurfaces.

The conductive species used in a homogeneous coating composition caninclude, but are riot limited to, salts of organic sulfonic acid such assodium sec-alkane sulfonate (ARMOSTAT® 3002 from AKZO Nobel) and sodiumC10-C18-alkane sulfonate (HOSTASTAT® HS1FF from Clariant), esters ofphosphoric acid such as STEPFAC® 8180, 8181, 8182 (phosphate esters ofalkyl polyethoxyethanol), 8170, 8171, 8172, 8173, 8175 (phosphate estersof alkylphenoxy polyethoxyethanol), POLYSTEP® P-11 P-12 P-13 (phosphateesters of tridecyl alcohol ethoxylates), P-31, P-32, P-33, P-34, P-35(phosphate esters of alkyl phenol ethoxylates), all available fromStepan Corporation, esters of fatty acids such as HOSTASTAT® FE20liqfrom Clariant (Glycerol fatty acid ester), ammonium or phosphonium saltssuch as benzalkonium chloride,N-benzyl-2-(2,6-dimethylphenylamino)-N,N-diethyl-2-oxoethanaminiumbenzoate, cocamidopropyl betaine, hexadecyltrimethylammonium bromide,methyltrioctylammonium chloride, and tricaprylylmethylammonium chloride,behentrimonium chloride (docosyltrimethylammonium chloride),tetradecyl(trihexyl)phosphonium chloride,tetradecyl(trihexyl)phosphonium decanoate,trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate,tetradecyl(trihexyl)phosphonium dicyanamide,triisobutyl(methyl)phosphonium tosylate, tetradecyl(trihexyl)phosphoniumbistriflamide, tetradecyl(trihexyl)phosphonium hexafluorophosphate,tetradecyl(trihexyl)phosphonium tetrafluoroborate, ethyltri(butyl)phosphonium diethylphosphate, etc.

The homogeneous composition can be prepared by mixing the conductivespecies in a liquid UV curable polymer to form a solution, and thenadding photoinitiators into the solution. The final homogeneous ITBcoating layer can include conductive species ranging from about 1% toabout 40%, or ranging from about 5% to about 30%, or ranging from about10% to about 20% by weight of the total homogeneous ITB layer.

The ITB coating layer can be formed by, for example, first providing acoating composition 105 in the dip tank 110, as seen in FIG, 1. Thecoating composition can include liquid UV curable polymers, conductivematerials including the conductive fillers, and/or the conductivespecies as described above, photoinitiator(s) and/or other additives.

The substrate 120 can be selected depending on specific ITBconfigurations. For example, the substrate 120 can include conventionalcylindrical mandrels. The substrate 120 can also include non-cylindricalmandrels on which ITB coating layers can be formed with more efficientdipping. The formed ITBs are seamless. For example, the non-cylindricalsubstrate can have a cross sectional shape including, but not limitedto, a rectangle, a square, a star, a triangle, or other shapes. Inembodiments, the substrate 120 can be made of any supporting materialincluding, for example, plastic, metal, glass, ceramic, semiconductor,wood, metal, and/or a mixture thereof.

The substrate 120 can have a desirable large area for simultaneouslyforming one or more ITBs thereon. In embodiments, a single dip tank canbe used. The single dip tank can have suitable dimensions to accommodatethe large area substrate.

FIGS. 2A-2B depict exemplary ITB substrates 120A-B selected for formingvarious ITBs 250 in accordance with various embodiments of the presentteachings.

The ITB substrates 120A-B can be selected to have suitable dimensions toaccommodate one or more ITBs 250 to be formed thereon. In FIG. 2A, asingle ITB 250 can be formed on the ITB substrate 120A. In FIG. 26, aplurality of ITBs 250 can be simultaneously formed on the ITB substrate1206 with each ITB 250 having same or different dimensions.

Each ITB 250 can have a belt width ranging from about 8 to about 40inches, or from about 10 to about 36 inches, or from about 10 to about24 inches. Each ITB 250 can have a length or circumference ranging fromabout 8 to about 60 inches, or from about 10 to about 50 inches, or fromabout 15 to about 35 inches.

The plurality of ITBs 250 shown in FIG. 28 can be arranged in arrays,for example, having a center-to-center spacing between adjacent ITBs offrom about 10 inches to about 200 inches, or from about 20 inches toabout 150 inches, or from about 30 inches to about 100 inches.

Referring back to FIG. 1, the ITB substrate 120 can be immersed in theliquid coating composition 105 for a period of time to form a coatingcomposition covered (or coated) substrate, which can then be withdrawnfrom the liquid coating composition 105. Upon exiting the dip tank 110,the composition coated substrate can enter the UV-curing chamber 130.

The thickness of each coating layer can be determined by, e.g.,dip-coating time, composition viscosity, withdrawing speed, UVwavelength, UV power, and/or UV-curing time.

The liquid coating composition 105 can have a viscosity ranging fromabout 60 centipoises to about 1,500 centipoises, or ranging from about150 centipoises to about 1,000 centipoises, or ranging from about 300centipoises to about 700 centipoises. In embodiments, the dip-coatingcan be performed for a time length ranging from about 1 minute to about20 minutes, or ranging from about 2 minutes to about 15 minutes, orranging from about 3 minutes to about 10 minutes.

The coated substrate can be withdrawn from the coating composition at aconstant speed ranging from about 10 to about 400 millimeters perminute, or ranging from about 50 to about 300 millimeters per minute, orranging from about 100 to about 200 millimeters per minute.Alternatively, the coated substrate can be withdrawn from the coatingcomposition at a speed programmed to minimize gravity effects at thebeginning and the end of the withdrawal. For example, the withdrawingspeed can be linearly decreased from the beginning to the end tomaintain desired coating thickness uniformity.

Upon entering the UV-curing chamber 130, the coating composition coveredsubstrate can be UV-cured. Depending on the UV curable polymers and thephotoinitiators used, the UV-curing process can be conducted at awavelength, for example, ranging from about 200 nm to about 400 nm,including from about 240 nm to about 370 nm, or from about 270 nm toabout 340 nm.

The UV-curing can be performed for a period of time, for example,ranging from about 1 second to about 600 seconds, or ranging from about5 seconds to about 300 seconds, or ranging from about 10 seconds toabout 120 seconds.

After a first cycle of dip-coating and UV-curing to form a first coatinglayer of UV cured polymer on the substrate, additional formation cyclescan be repeated on the first UV cured coating layer such that aplurality of coating layers can be stacked on the substrate to provide adesirable thickness. For example, the UV cured substrate having thefirst coating layer can be re-immersed into the liquid coatingcomposition in the dip tank for a second dip-coating process. Thesubstrate having a composition coated first coating layer can then beremoved from the liquid coating composition and then enter the UV-curingchamber for a second UV-curing to form a second UV cured coating layeron the first coating layer until a desired thickness is achieved.

In contrast, conventional methods of forming ITBs may include adip-coating followed by a lengthy air or oven-drying, with substantialgravity effects that give rise to a non-uniform thickness. Because theUV-curing can be performed at high-speeds in shorter time periods,limited sagging may occur due to the gravity effects. ITB formed usingthe exemplary methods disclosed herein can then have uniform thickness.That is, the combination of dip-coating with UV-curable coatingmaterials can allow for control of thickness as well as thicknessuniformity. In embodiments, the thickness of ITB can be uniform, forexample, within a range of ±3 microns.

Additionally, because the previous coating layer is already UV cured,e.g., by a UV cross-linking, re-immersion of the coated substrate intocoating composition in the dip tank does not result in dissolution ofthe previously cured layer. In contrast, multiple formation cycles cannot be used in conventional methods of forming ITBs, because there-immersion of the thermally cured layer into the coating compositioncan dissolve the previously formed layer.

Further, the UV-curing process can be environmentally friendly, e.g.,producing little VOC (Volatile organic compounds) and consuming lowenergy. UV-curing can also provide resistance to stains, abrasions, andsolvents, and can provide superior toughness. UV-curing can also providehigh gloss compared with other coating methods.

In embodiments, the final coating layer can be parted, delaminated orreleased from the substrate and configured in a printer. The substrate120 can also be surface treated prior to dipping into the coatingcomposition so as to facilitate the later release of the formed ITBcoating layer. Various releasing agents or parting agents known to oneof ordinary skill in the art can be used.

The volume (or bulk) resistivity and the surface resistivity of thefinal ITB coating layer can be uniform with minimal variation. Forexample, a maximum value of volume resistivity can be within the rangeof 1 to 10 times the minimum value, and a maximum value of surfaceresistivity can be within the range of 1 to 100 times the minimum value.

The formed ITB can have a surface resistivity ranging from about 10⁸ohms/sq to about 10¹³ ohms/sq, or ranging from about 10⁹ ohms/sq toabout 10¹² ohms/sq, or ranging from about 10¹⁰ ohms/sq to about 10¹¹ohms/sq. In embodiments, the formed ITB coating can have a mechanicalYoung's modulus ranging from about 500 MPa to about 10,000 MPa, orranging from about 1,000 MPa to about 5,000 MPa, or ranging from about1,500 MPa to about 3,000 MPa.

In embodiments, the formed ITB can also have multi-layer configurations.For example, a two-layer configuration can include an outer releaselayer disposed on the ITB. The outer release layer can include polymerssuitable for release such as fluoropolymers or others as known to one ofordinary skill in the art. In another example, a three-layerconfiguration can include an outer release layer disposed on aconformable layer (e.g., silicone rubber), that is disposed on the ITB.In embodiments, other additional functional layers, for example,adhesive layers, can also be formed over the ITB.

In embodiments, the disclosed ITBs and method of their formation caninclude the materials and methods disclosed in co-pending U.S. patentapplications, Ser. No. 12/624,589, filed Nov. 24, 2009, and entitled “UVCured Heterogeneous Intermediate Transfer Belts (1TB),” and Ser. No.12/731,449, filed Mar. 25, 2010, and entitled “Intermediate TransferBelts,” which are hereby incorporated by reference in their entireties.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. In addition, while a particular feature of thepresent teachings may have been disclosed with respect to only one ofseveral implementations, such feature may be combined with one or moreother features of the other implementations as may be desired andadvantageous for any given or particular function. Furthermore, to theextent that the terms “including,” “includes,” “having,” “has,” “with,”or variants thereof are used in either the detailed description and theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising.”

Further, in the discussion and claims herein, the term “about” indicatesthat the value listed may be somewhat altered, as long as the alterationdoes not result in nonconformance of the process or structure to theillustrated embodiment. Finally, “exemplary” indicates the descriptionis used as an example, rather than implying that it is an ideal.

Other embodiments of the present teachings will be apparent to thoseskilled in the art from consideration of the specification and practiceof the present teachings disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the present teachings being indicated by thefollowing claims.

What is claimed is:
 1. An intermediate transfer belt (ITB) comprising:one or more coating layers stacked together to provide the ITB, whereinthe ITB has a surface resistivity ranging from about 10⁸ ohms/sq toabout 10¹³ ohms/sq, and a thickness ranging from about 30 microns toabout 500 microns with a thickness uniformity within a range of ±3microns, and wherein each coating layer of the one or more coatinglayers comprises a UV cured polymer.
 2. The ITB of claim 1, wherein theUV cured polymer comprises a compound selected from the group consistingof a monomeric acrylate, an oligomeric acrylate and a combinationthereof.
 3. The ITB of claim 2, wherein the monomeric acrylate isselected from the group consisting of trimethylolpropane triacrylate,hexandiol diacrylate, tripropyleneglycol diacrylate, dipropyleneglycoldiacrylate, and a combination thereof.
 4. The ITB of claim 2, whereinthe oligomeric acrylate is selected from the group consisting ofurethane acrylate, polyester acrylate, epoxy acrylate, polyetheracrylate, olefin acrylate comprising polybutadiene acrylate and acombination thereof.
 5. The ITB of claim 4, wherein the oligomericacrylate is urethane acrylate.
 6. The ITB of claim 1 wherein eachcoating layer comprises one or more conductive fillers.
 7. The ITB ofclaim 6, wherein the one or more conductive fillers is in an amountranging from about 0.2% to about 30% by weight of the total coatinglayer.
 8. The ITB of claim 7, wherein the one ore more conductivefillers is selected from the group consisting of carbon blacks, carbonnanotubes, fullerenes, polyanilines, stannic oxides, indium oxides,potassium titanates and combinations thereof.
 9. The ITB of claim 7,wherein the one or more conductive fillers comprises carbon nanotubes.10. The ITB of claim 1, wherein each coating layer comprises one or moreconductive species.
 11. The ITB of claim 10, wherein the one or moreconductive species is in an amount ranging from about 1% to about 40% byweight of the total coating layer.
 12. The ITB of claim 10, herein theconductive species is selected from the group consisting of salts oforganic sulfonic acid, esters of phosphoric acid, esters of fatty acids,ammonium or phosphonium salts and combinations thereof.
 13. The ITB ofclaim 1, wherein the ITB has a belt width ranging from about 8 inches toabout 40 inches and a circumference ranging from about 8 inches to about60 inches.
 14. The ITB of claim 1, wherein the ITB has a Young's modulusranging from about 500 MPa to about 8,000 MPa.
 15. The ITB of claim 1,wherein the stacked coating layers have a combined thickness rangingfrom about 70 to about 120 microns.
 16. The ITB of claim 1, wherein theITB is seamless.
 17. The ITB of claim 1, wherein the ITB furthercomprises an outer release layer disposed over the UV cured polymer. 18.The ITB of claim 1, where the ITB further comprises an outer releaselater disposed over a conformable layer that is disposed over the UVcured polymer.
 19. The ITB of claim 1, wherein a surface resistivity ofthe ITB ranges from about 10¹⁰ ohms/sq to about 10¹¹ ohms/sq.